Providing power for robotic surgical systems

Imagine major surgery performed through tiny incisions, with much less pain, a shorter hospital stay, faster return to normal activities and the potential for better clinical outcomes. Until recently, options for surgery have been limited and included traditional open surgery with a large incision or, a procedure that uses a lighted tube put through a small incision called laparoscopic surgery. However, even though laparoscopic surgery is a minimally invasive surgery, it is often limited to very simple procedures due to the instruments required. Thanks to breakthrough technology, there is another category of minimally invasive surgery that incorporates robotic assistance.

These types of surgical systems combine a computer and robotic technologies that create a robotic-assisted laparoscopic, thoracoscopic or endoscopic surgery. By providing surgeons with enhanced capabilities, it is possible to treat a broader range of conditions using a minimally invasive approach with better visualization, precision, dexterity and control than possible through traditional surgical approaches.

Minimally invasive robotic-assisted surgery has been used in everything from heart surgery to cancer surgery, to treat conditions as diverse as prostate cancer, endometrial cancer, morbid obesity and mitral valve regurgitation. These systems combine robotics and surgical technology as never before, enabling surgeons to provide the most effective and least invasive treatment option available for a wide range of complex conditions.

The typical set up is a surgeon's console, a patient cart with interactive robotic arms and a highly magnified 3D image monitor of the body’s interior. New methods of imaging and image-guidance technology provide surgeons with very accurate three-dimensional information about the location of critical subsurface structures and instrument position.

To operate, the surgeon uses master controls that work like forceps. As the surgeon manipulates the controls, the system responds to the input in real time, translating his or her hand, wrist and finger movements into precise movements of miniaturized instruments. Figure 1 shows a picture of a robotic surgical system.

Figure 1: Typical robot-assisted surgical machine

This type of system is usually designed, using distributed power architecture. Therefore, it operates from the AC mains, consisting of either 110VAC or 220VAC and is converted to an isolated 48V DC voltage that charges a bank of 48V batteries. This 48V bus voltage is routed throughout the system to power downstream point of load regulators for all the subsystems, including the robotic arms, system electronics, instruments and a high resolution display. The battery pack maintains system operation when a loss of AC mains occurs. However, depending on the state of charge of the batteries, the battery pack voltage can be above, below or equal to the 48V input making it a challenge to design a power supply for this application. Linear Technology has recently released the LT8705, an 80V synchronous buck-boost controller that addresses the needs of such a power supply requirement.